Authorities consider the doomed Malaysia Airlines Flight 370, missing for more than two weeks, to be lost "beyond any reasonable doubt" somewhere in the Indian Ocean, with all passengers and crew assumed to have perished.

The fate of the missing plane has captivated the world since March 8, when the Beijing-bound Boeing 777-200 vanished mysteriously from civilian radar screens, less than an hour after departing Kuala Lumpur.

Families of the 239 missing passengers received a text message from the airline with the information, according to a CNBC producer who saw a copy of the message."We deeply regret that we have to assume beyond any reasonable doubt that the MH370 has been lost and that none of those on board have survived," the message read.

(The airline, facing a backlash over the use of text messaging, later clarified that families had also been contacted in person and by phone, and that texts had only been used to supplement that).

At a press conference on Monday in Kuala Lumpur, Malaysian Prime Minister Najib Razak delivered a terse statement. According to new information, the flight was most likely at the bottom of the sea, though the circumstances behind its disappearance were still unclear.

"It is therefore with deep sadness and regret that I must inform you that according to this new data, MH370 ended in the southern Indian Ocean," said Razak, delivering the news that grief stricken friends and relatives had been dreading for days. He said a new analysis of satellite data indicates the missing plane was lost in a remote area of the world's third largest water body, which spans more than 28 million square miles.

No confirmed sighting of the plane has been made since its disappearance, though unconfirmed reports have claimed to have spotted debris.

Malaysia Airlines said in a statement to the families that "our prayers go out to all the loved ones of the 226 passengers and of our 13 friends and colleagues at this enormously painful time."

"We know there are no words that we or anyone else can say which can ease your pain," the airline said. "The ongoing multinational search operation will continue, as we seek answers to the questions which remain."

--By CNBC.com. Reuters and The Associated Press contributed to this story.